EP3327450A1 - Device and method for investigating insulating wire coatings - Google Patents

Abstract

Device (21) and method for inspecting insulating wire coatings (2) on a moving electrically conductive wire (1) - a high voltage generating unit (6) a measuring electrode (4) a grounding electrode (3) which grounds the wire (1), - A microprocessor (8) for data processing - And a measuring unit (31) which measures the measuring current (30), which flows through the measuring electrode (4), and / or the measuring voltage (5) between the measuring electrode (4) and ground electrode (3) and the measured current and / or voltage values are made available to the microprocessor (8), wherein the microprocessor (8) is set up to monitor the current and / or voltage values detected via the measuring unit (31) over at least one short time window (17) and at least one long time window (15 ) to detect increases in the measuring current (30) and / or drops in the measuring voltage (5).

Description

The invention relates to a device for the examination of insulating wire coatings on a moving electrically conductive wire with a high voltage generating unit, a measuring electrode, a ground electrode which grounds the wire, a microprocessor for data processing and a measuring unit which measures the measuring current flowing through the measuring electrode and / or measures the measurement voltage between the measurement electrode and ground electrode and provides the measured current and / or voltage values to the microprocessor.

• Anbringen einer Erdungselektrode an den Draht;
• Anlegen einer Spannung aus einer Hochspannungserzeugungseinheit an die Drahtbeschichtung;
• Messen des Messstroms, der über die Messelektrode fließt, und/oder der Messspannung zwischen Messelektrode und Erdungselektrode.

Furthermore, the invention relates to a method for investigating insulating wire coatings on an electrically conductive wire with the steps:

• Attaching a ground electrode to the wire;
• Applying a voltage from a high voltage generating unit to the wire coating;
• Measuring the measuring current that flows through the measuring electrode, and / or the measuring voltage between the measuring electrode and ground electrode.

Coated wires, such as those required in the production of coils, chokes, motors or transformers, require the insulation properties of the coated wires to be guaranteed to ensure correct operation and safety. As a result, the insulation properties of the wire being coated are already checked at the end of the coating process. Thus, a conductive wire, e.g. made of copper or aluminum, a wire coating applied and then tested their error-free insulation.

For this purpose, a voltage is usually applied between the conductive wire and the exterior of the wire coating, which causes no or a non-measurable current in the idealized error-free case. However, if, for example, the wire coating is defective at one location, i. not or only partially present or violated in their homogeneity, then there is a measurable current flow.

Will now be the wire coating of a wire that is in conductive Connection with the grounding electrode, brought into contact with the measuring electrode, so it comes under idealized conditions only to a measuring current, if the insulation is defective. Under real conditions, despite the faultless insulating wire coating, a measuring current is already flowing, since the wire coating is a dielectric and therefore the wire and the wire coating act similarly as a cylindrical capacitor. This measuring current therefore represents a charging current. If the wire is now moved steadily, then it comes to a permanent charging current, which charges the wire and the detection of errors in the wire coating difficult because the charging current is also present in a faultless wire coating. Due to the capacitive properties of the wire coating, a current flow occurs which makes it considerably more difficult to correctly detect defects in the wire coating.

In spite of this, independent of the intactness of the wire coating current flow, on the measurement of current values to draw a conclusion on the quality of the wire coating, various approaches have been proposed in the prior art.

The EP 2 251 179 A1 discloses, for example, an apparatus for testing a moving coated wire having a precharge electrode, a sensing electrode spaced from the precharge electrode, and a wire ground. The precharge electrode applies a voltage between the coating and the conductive wire core that polarizes the coating. As the wire is fed further to the measuring electrode, the polarization and thus the voltage on the coating reduces exponentially. By means of a corresponding device, the measuring electrode has a voltage which corresponds to the voltage of the now continued wire. As a result, defects in the coating, which show up by an increased current flow across the measuring electrode, to be better recognized.

However, such a current measurement is relatively complicated and complicated, since two electrodes must be attached, the voltage must be precisely matched via special devices in order to minimize capacitive compensation currents.

The object of the present invention is therefore to provide a structurally simple device or a comparatively simple method for the examination of coated wires, which detects errors in the wire coating reliably despite the disturbing capacitive currents.

According to the invention this is achieved in a device of the type mentioned above in that the microprocessor is set up to average the current and / or voltage values detected via the measuring unit over at least one short time window and at least one long time window in order to increase the measuring current and / or or detect break-in of the measuring voltage.

For this purpose, the measuring voltage is essentially made available with the aid of the high-voltage generating unit and applied via the measuring electrode to the wire coating of the grounded wire passed by.

With the aid of the averaging of the current values in at least a relatively long time window, the (continuous) current flowing through the wire movement can be determined. In this case, these time windows preferably slide over an adjustable number or an adjustable period of time to measured current values, which are preferably read in regularly, and thus continuously generate a current mean value for the measuring current.

With the aid of the averaging of the voltage values in at least a relatively long time window, the mean measuring voltage can be determined. These time windows preferably slide over an adjustable number or an adjustable time period to measured voltage values, which are preferably read in regularly, and thus continuously generate a current mean value for the measurement voltage.

The at least one long time window for the measuring current represents a measure of the mean charging current, since short-term fluctuations of the current are averaged out. The charging current is at constant conditions, such as the geometry of the wire and the wire coating, the applied measuring voltage or the speed of the passing coated wire, etc., substantially constant.

The at least one short time window for the measuring current, however, shows comparatively short-term changes in the measuring current, which arise due to changes in the wire coating. This may be, for example, a change in thickness or a lack of wire coating. For the measuring voltage, however, it is true that this is reduced at an increased measuring current, for example due to voltage drops at (internal) resistors. The at least one long time window for the measurement voltage represents a measure of the mean measurement voltage. The at least one short time window represents a measure of short-term voltage changes which occur in the case of errors in the wire coating. Thus, two sizes, current and voltage, are available to detect errors in the wire coating.

In a preferred embodiment, the mean value of the at least one long time window is subtracted from the mean value of the at least one short time window. The result in the time windows for the measuring current is a measure of a fault current, which gives information about errors in the wire coating. This fault current represents the deviation of the short-term mean value, determined for at least one long time window, from the long-term and therefore essentially comparatively constant mean value determined at least for a long time window. This deviation is caused by errors in the thickness of the wire coating since additional or less charge current is necessary , a voltage breakdown takes place or in the total absence of the wire coating, a short circuit is present.

Advantageously, exactly one short and exactly one long time window is provided for the measuring current and / or the measuring voltage. The length of the short time window is preferably between 0.5 ms and 5 ms, in particular substantially 1 ms. The length of the long time window is preferably between 10 ms and 500 ms, in particular substantially 100 ms.

Furthermore, it is favorable if the lengths of exactly one short time window and of exactly one long time window differ by at least a factor of 10, preferably by a factor of 100.

The device preferably has a control and / or regulating unit which can regulate or control the measuring voltage between the measuring electrode and the grounding electrode to a predetermined reference value. For this purpose, for example, a PI controller is provided whose output controls the high voltage generating unit. The reference value for the PI controller can be specified by the microprocessor. For this purpose, the microprocessor may have a digital / analog converter.

For a suitable control, it is expedient for the control and / or regulating unit, as the feedback variable, to provide a variable proportional to the measuring voltage applied between the measuring electrode and ground electrode. For example, this may be substantially the same voltage that is provided to the microprocessor as the measurement voltage. This voltage can be read by the microprocessor via an analog / digital converter.

Preferably, the control and / or regulating unit can have a current limiting, which limits the measuring current, which flows via the measuring electrode, to a maximum permissible current by changing the measuring voltage. For this purpose, a further control or regulating device may be provided, which influences the high-voltage generating unit. A feedback variable for this further control or regulating unit can essentially be the same current or a voltage which is proportional thereto and which is made available to the microprocessor as a measuring current. Furthermore, a limiting resistor may be present between the high-voltage generating unit and the measuring electrode, limiting the measuring current in the event of a short circuit and faulty current limiting.

Furthermore, it is advantageous if the current limit adjustable is. For example, the maximum permissible measuring current can be predetermined by the microprocessor.

The device may also comprise a speed detection of the wire. For this purpose, for example, an incremental encoder or an inductive initiator of pulses may be provided. For example, the wire is passed over a roller whose speed is read in via pulses and made available to the microprocessor. These can be measured, for example, optically or inductively, depending on the method. Thus, knowing the geometry of the assembly, the speed of the wire can be determined.

Preferably, the high voltage generation unit for converting different voltage levels may have a lower voltage lower side and a higher high voltage side.

In order to ensure fast measuring current detection, it is favorable if the measuring unit measures the measuring current and the measuring voltage on the high-voltage side, because due to capacities and possible filters the current on the low-voltage side changes more slowly than the measuring current on the high-voltage side.

In order to bring the measuring electrode in contact with the wire coating, this can be designed as a measuring roller or as a measuring brush, in particular made of carbon fiber. This is then brought into abrading contact with the wire coating. Furthermore, the measuring electrode can contact the wire coating over the entire wire circumference by being formed around the wire and thus evenly touched. For this purpose, the measuring electrode has a multi-part offset and touches the wire from different sides. As a result, errors in the wire coating can be reliably detected.

The measuring current across the measuring electrode can be measured essentially in a range of 0 to 200 μA, in particular with a resolution of 0.1 μA. This can be measured by means of a shunt resistor, at which the voltage drop is measured according to the measuring current, and correspondingly precise operational amplifiers be determined.

In order to be able to provide the data which the microprocessor ascertains and processes to other devices, an interface, for example a LAN interface, can be provided for communication with a further device, in particular data processing devices such as computers.

The high voltage unit may be a DC / DC converter to convert the DC voltage on the low voltage side, which has a lower voltage level, to a higher voltage level on the high voltage side. The DC / DC converter is advantageously variably adjustable.

• Kalibrieren der Hochspannungserzeugungseinheit:
  • Dazu wird die Hochspannungserzeugungseinheit auf geeignete Messspannungswerte eingestellt, welche anschließend mit einem externen Hochspannungsvoltmeter gemessen werden. Die Vorgaben des Mikroprozessors werden gemäß den mit dem Hochspannungsvoltmeter gemessenen Werten korrigiert. Zwischen den so ermittelten Messpunkten liegende Spannungswerte können durch lineare Interpolation vorgegeben werden.
• Kalibrieren Messeinheit:
  • Nach Kalibrierung der Hochspannungserzeugungseinheit wird an geeigneten Punkten eine Messspannung vorgegeben und durch die Messseinheit erfasst. Die dem Mikroprozessor von der Messeinheit zur Verfügung gestellten Messspannungen werden mit dem Hochspannungsvoltmeter verglichen und dementsprechend korrigiert. Nach der durchgeführten Kalibrierung der Messspannung können dazwischen liegende Messspannungen durch lineare Interpolation ermittelt werden.

In order to minimize errors due to tolerances in the component production of the device according to the invention, in this embodiment, a calibration process for the measuring unit and the high voltage generating unit can be provided. This includes the following steps:

• Calibrating the high voltage generation unit:
  • For this purpose, the high voltage generation unit is set to suitable measured voltage values, which are then measured with an external high voltage voltmeter. The specifications of the microprocessor are corrected according to the values measured with the high-voltage voltmeter. Voltage values between the measuring points determined in this way can be specified by linear interpolation.
• Calibrate measuring unit:
  • After calibration of the high-voltage generating unit, a measuring voltage is predetermined at suitable points and detected by the measuring unit. The measuring voltages provided to the microprocessor by the measuring unit are compared with the high-voltage voltmeter and corrected accordingly. After calibration of the measuring voltage, intermediate measuring voltages can be determined by linear interpolation.

Subsequently, the detection of the measuring current is corrected. For this purpose, two suitable measuring currents are given, for example by two different resistances between the measuring electrode and the earth electrode. The measured and the predetermined values are compared and corrected accordingly. Intermediate measured current values can again be determined by linear interpolation.

The inventive method of the type mentioned is characterized in that the detected current and / or voltage values are averaged over at least a short time window and at least one long time window to detect increases in the measured current and / or dips in the measured voltage. In order to avoid repetition, reference is made to the above statements in connection with the device according to the invention with regard to the advantages of the method according to the invention. Same advantages and effects arise in the inventive method.

• Fig. 1 eine schematische Darstellung eines Drahtes mit Drahtbeschichtung im Querschnitt;
• Fig. 2a eine perspektivische Ansicht eines Ausschnitts einer Drahtlackiervorrichtung mit der erfindungsgemäßen Vorrichtung;
• Fig.2b eine perspektivische Übersichtdarstellung einer Drahtlackiervorrichtung mit der erfindungsgemäßen Vorrichtung;
• Fig. 3 einen Schaltplan einer erfindungsgemäßen Vorrichtung;
• Fig. 4a und 4b grafische Darstellungen der gemessenen Stromwerte vor und nach Subtraktion der gemittelten Stromwerte des langen Zeitfensters.

The invention will be explained in detail below with reference to a preferred embodiment, to which it should by no means be restricted. The figures show in detail:

• Fig. 1 a schematic representation of a wire with wire coating in cross section;
• Fig. 2a a perspective view of a section of a Drahtlackiervorrichtung with the device according to the invention;
• 2b an overview perspective view of a Drahtlackiervorrichtung with the device according to the invention;
• Fig. 3 a circuit diagram of a device according to the invention;
• Fig. 4a and 4b Graphical representations of the measured current values before and after subtraction of the averaged current values of the long time window.

Fig. 1 shows a schematic diagram of a conductive wire 1 with an insulating wire coating 2 in cross section.

The wire 1, which consists for example of copper or aluminum, is connected via the ground electrode 3 to the common ground potential 12 of the device (not shown). Furthermore, the wire coating 2 is in contact with a measuring electrode 4, which covers the entire circumference of the wire coating. This is provided in this embodiment as a measuring brush. Between the measuring electrode 4 and the grounded wire 1, the measuring voltage 5 is applied. Therefore, a measuring voltage occurs between a common ground potential of the device and the measuring electrode 4, which drops substantially at the insulating wire coating in the fault-free case. The measuring electrode 4 is brought into contact with the wire coating 2 of the wire 1 guided past the measuring electrode 4. On the underside of the wire, the coating has an error 2a.

Fig. 2a shows a Drahtlackiervorrichtung with the inventive devices 21st

The grounding electrode 3 is a conductive brush, which is made of carbon fiber, for example, whose conductive bristles loop over a conductive roller 28, with which the still uncoated wire 1 is continued and thus is in conductive contact therewith. On the other hand, the ground electrode 3 is in turn connected to the common ground potential of the device. Accordingly, the conductive uncoated wire is conductively connected to the common ground potential of the device.

After the uncoated wire 1 has been provided with a wire coating device 2 with a wire coating device, which is known from the prior art, it is guided by means of wire-guiding rollers 20 to the measuring electrode 4, which in this embodiment is a measuring brush. The conductive bristles of the measuring brush 4 are thus in contact with the wire coating 2 and thus connect the wire coating 2 conductive with the measuring unit 31 (s. Fig. 3 ). The measuring unit 31 can thus the measuring current 30 and / or between the measuring brush 4 and ground electrode 3 occurring measuring voltage and over the Measuring brush 4 flowing measuring current 30 determine.

The speed of the wire can be detected and read via a speed detection 32 by means of inductive pulses of the wire-guiding roller 20. The inductive pulses can be detected via an inductive sensor and the signals are made available to the microprocessor 8.

Fig. 2b shows the device 21 according to the invention in an exemplary arrangement with the components of a wire coating device. For this purpose, the wire 1 is first brought to a desired diameter in a drawing machine 22 and then passed into a anneal 23, where the structure of the wire 1 recrystallized. The wire is then provided with the aid of a lacquer ware 24 with a coating 2, which is cured in a drying oven 25. The wire 1 can also be passed several times through parts of the Drahtlackiervorrichtung. For cooling the wire, a wire cooler 26 is further provided. To investigate the wire coating 2, the wire 1 is guided to the device 21 according to the invention and then wound onto rewinders 27.

Fig. 3 shows the circuit diagram of a preferred embodiment with a high voltage unit 6, a low voltage side 33 and a high voltage side 19. The high voltage generation unit is in this embodiment, a DC / DC converter 36. The voltage at the high voltage side 19 of the high voltage generating unit 6 substantially corresponds to the measurement voltage 5. Die Measuring unit 31 can also be seen.

Also visible is the voltage measurement 7, which determines the measurement voltage via a voltage divider and after conversion to a suitable voltage level provides a microprocessor 8. This can read voltages via analog / digital converter.

Furthermore, a voltage control 9 is provided, which controls the high voltage unit 6 according to the specifications of the microprocessor. The high voltage generating unit 6 is provided around a (not shown) measuring electrode 4, a voltage of substantially between 300 volts and 4000 volts.

A current measurement 10 and a current limiting 11 are also provided, which regulates the maximum measuring current. For this purpose, the voltage at the high-voltage side 19 of the high-voltage generating unit 6 is reduced to a high measuring current 30 so far that the measuring current 30 does not exceed a predetermined value from the microprocessor. For this purpose, the current limitation comprises a control unit which also controls the high voltage generating unit 6. The feedback variable used is essentially the measuring current.

A ground potential 12 is connected both to the ground electrode 3 and to the current measurement 10, the voltage measurement 7, the current limit 11 and the microprocessor 8.

For the determination and the subsequent processing of the voltage values of the measuring voltage in the microprocessor 8, the measuring voltage can be reduced to a voltage level suitable for the microprocessor 8 with the aid of voltage dividers 13 and other auxiliary means, such as operational amplifiers and their circuitry. The microprocessor 8 detects the voltage values and discretizes them via an analog-to-digital converter.

The current measurement is carried out via a shunt resistor 14. The voltage dropping across the shunt resistor 14 is then a measure of the measuring current. In order to bring the voltage dropping at the shunt resistor 14 to a voltage level suitable for the microprocessor, voltage dividers 13 and aids such as operational amplifiers and their circuitry are again provided.

Fig. 4a shows an exemplary application of the device to a guided past the measuring electrode wire 1.2.

On the abscissa, the length is plotted in meters, as can be calculated, for example, from the speed of the speed detection 32 and the past time, on the ordinate, the calculated (average) current 34 is shown in microamps. The calculated (average) current 34 settles from overlaps of the mean values of the at least one long time window 15 and the at least one short time window 17, which were also converted into meters.

In Fig. 4a the mean value 35 of the measuring current 30 is shown, as determined by the at least one long time window 15. The current peak 16 is a mean value determined by the at least one short time window 17 and can be caused, for example, by a defective wire coating 2, as described in US Pat Fig. 1 can be seen at the error 2a. In the preferred embodiment, there is exactly one short and one long time window.

In Fig. 4b is then the fault current 18 shown. The fault current 18 is determined by a subtraction of the short from the long time window, and thus represents a measure of the changes of the wire coating 2.

Claims (15)

Device (21) for inspecting insulating wire coatings (2) on a moving electrically conductive wire (1) - a high voltage generating unit (6) a measuring electrode (4) a grounding electrode (3) which grounds the wire (1), - A microprocessor (8) for data processing - And a measuring unit (31), which measures the measuring current (30), which flows through the measuring electrode (4), and / or the measuring voltage (5) between the measuring electrode (4) and ground electrode (3) and the measured current and voltage values the microprocessor (8) is available, characterized in that the microprocessor (8) is adapted to the over the measuring unit (31) detected current and / or voltage values over at least a short time window (17) and at least one long time window ( 15) in order to detect increases in the measuring current (30) and / or drops in the measuring voltage (5). Device according to claim 1, characterized in that the calculated mean values (35) of the current and / or voltage values of the at least one long time window (15) are determined by the mean values (16) of the current and / or voltage values of the at least one short time window (17 ) are subtracted. Apparatus according to claim 2, characterized in that exactly one short time window (17), which preferably has a duration between 0.5 ms and 5 ms, in particular substantially 1 ms, and exactly one long time window (15), which preferably has a duration of 10 ms to 500 ms, in particular substantially 100 ms, is provided. Device according to claim 3, characterized in that vary the lengths of precisely a short time window (17) and exactly one long time window (15) at least by a factor 10, preferably by a factor of one hundredth Device according to one of claims 1 or 4, characterized in that the device (21) has a control and / or Control unit (9) which is adapted to regulate or control the measuring voltage (5) between the measuring electrode (4) and the grounding electrode (3) to a predetermined reference value. Apparatus according to claim 5, characterized in that the control and / or regulating unit (9) is provided as a feedback variable one of the voltage applied between the measuring electrode and ground electrode measuring voltage (5) proportional size available. Device according to one of claims 5 or 6, characterized in that the control and / or regulating unit (9) has a current limiting (11), which the measuring current (30), which flows via the measuring electrode (4), by changing the measuring voltage (5) limited to a maximum allowable current. Apparatus according to claim 7, characterized in that the maximum current of the current limiting (11) is adjustable. Device according to one of claims 1 to 8, characterized in that the device (21) has a speed detection (32) of the wire (1). Device according to one of claims 1 to 9, characterized in that the high voltage generating unit (6) for converting different voltage levels has a lower voltage side (33) of lower voltage and a higher voltage side (19) of higher voltage and the measuring unit (31) the measuring current (30) and or the measuring voltage (5) on the high-voltage side (19) measures. Device according to one of claims 1 to 10, characterized in that the measuring electrode (4) is a measuring roller or a measuring brush, in particular made of carbon fiber, and touches the wire coating (2) over the entire wire circumference. Device according to one of claims 1 to 11, characterized in that the measuring current (30) across the measuring electrode (4) is substantially in a range from 0 to 200 microamps in particular measured at a resolution of about 0.1 μA. Device according to one of claims 1 to 12, characterized in that the device (21) is provided at least one interface for communication with other devices, in particular data processing devices such as computers. Device according to one of claims 1 to 13, that the high voltage generation unit (6) is a DC / DC converter (36). Method for testing insulating wire coatings (2) on an electrically conductive wire (1), comprising the steps of: - attaching a grounding electrode (3) to the wire (1) - applying a voltage from a high voltage generating unit (6) to the wire coating (2) - Measuring the measuring current (30) and / or the measuring voltage (5) between the measuring electrode (4) and ground electrode (3), which flows through the measuring electrode (4), characterized in that the detected current and / or voltage values over at least one short time window (17) and at least one long time window (15) are averaged to detect increases in the measuring current (30) and / or dips in the measuring voltage (5).

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